Regulator with bipolar transistors

ABSTRACT

A reference bias regulator utilizes both NPN and PNP transistors supplying a reference bias for constant current sources to be used as load devices in low voltage integrated circuits thus eliminating the necessity to use large ohmic value external resistors. The regulator effectively maintains a current independent of source and load variation.

United States Patent Williams July 1, 1975 REGULATOR WITH BIPOLAR3.577.167 /1971 Avins .1 307/296 3,612,984 /1971 Davis et al.... 323/9TRANSISTORS 0 3,629,692 12/1971 Goyer 323/4 [75] Inventor: Clark R.Williams, Da as. T 3,683,270 8/1972 Mattis 323/4 3,735,240 5 1973 D t323 4 [73] Assgneei Texas Instruments Inwrlmmedi 3753,0721 851973 32359Dallas, Tex.

[22] Filed: 1974 Primary ExaminerGerald Goldberg 2 App|l 44 ,233Attorney, Agent, or FirmHarold Levine; Edward J.

Connors, Jr.; Stephen S. Sadacca Related U.S. Apphcatlon Data [63]Continuation of Ser. No. 263,8l9, June [9, 1972,

abandoned. [5 7] ABSTRACT 52 Us Cl 323/4 307/297 307/299 B; A referencebias regulator utilizes bOlh NPN and PNP 323/9; 330/ D transistorssupplying a reference bias for constant cur- 511 lm. cu G05F 1/56 mm beused as load devices in low voltage [58] Field 0' Search 323/1 11 9, 22T; integrated circuits thus eliminating the necessity to use 307/296,297' 299 A, 299 B; 330/69 30 D large ohmic value external resistors. Theregulator effectively maintains a current independent of source {56]References Cited and load variation.

UNITED STATES PATENTS 8 Claims, 8 Drawing Figures 3,534,245 10/1970Limberg 323/4 w rvvv SUPPLY VOLTAGE REF. H1 P'zl'aE-q P5 RESISTOR a E gREFERENCE i TO SLAVE 5 2' REGULATOR 61 I 23 ne siign i 2 i ii F i 6 1?REF. TO 21918 g I i i l L 1 LL:

lo FROM CURREN T i SOURCE 1 13 REFERENCE m x I A %WTO SLAVE 43; START 53 /2|\ REGULATOR l 'I gi RESISTOR LJ+1 REF. TO 2|9l8 3 I '0 FROM CURRENTl L 'r SOURCE i REGULATE REHr'EHENCE I SUPPLY VOLTAGE I v+ DRIVE 2| J: Ir J REFERENCE-J l RESOSTOR s RESISTOR FROM CURRENT SOURCE REFERENCE Fig:a SUPPLY VOLTAGE SHEET 2 P+ ISOLATION New Fig.4A

Fig, 5

SUPPLY REFERENCE Fig, 6

TO MASTER REGULATOR 1 L l \\\\\\\x i 1 REGULATOR WITH BIPOLARTRANSISTORS This is a continuation of application Ser. No. 263,819,filed June 19, 1972. and now abandoned.

Low powered electronically controlled timekeeping devices have beendescribed in the literature. For example, one such device is describedin U.S. Pat. No. 3,560,998 and another in U.S. Pat. No. 3,505,804.

There have been proposals which suggest utilizing CMOS (complementarymetal oxide semiconductor) technology in combination with liquid crystaldisplays primarily due to the power savings capability of such aconfiguration. Certain advantages, however, may be obtained utilizingbipolar technology for implementing the circuit logic of electronicwatches; however, readily available battery sources provide on the orderof one volt and it is exceedingly difficult to implement logic withbipolar integrated circuits using such voltage levels. Additionallimitations are imposed due to integration requirements, these primarilybeing that it is difficult to obtain large resistances in integratedcircuit format.

An electronic watch overcoming many of the abovementioned problems isdisclosed in U.S. Patent application Ser. No. 264,212 filed June 19,1972 by Clark R. Williams and Robert H. Schnurr for ElectronicTimekeeping System", now U.S. Pat. No. 3,886,726, which disclosure ishereby incorporated herein by reference.

Briefly, in accordance with that invention, a timekeeping device isprovided which includes a battery operated bipolar integrated circuitfor regulating display of the time, including means for displaying andindependently setting the calendar date. A crystal controlled oscillatorgenerates a master frequency. This frequency is applied to a frequencydivider comprising a ripple counter of toggle flip-flops effective toproduce a one hertz system clock signal. The toggle flip-flopsrespectively comprise bipolar transistors in a circuit configurationeffective to operate from voltage sources which provide on the order ofone volt. The system clock is applied to a series of counters and decodelogic to effect generation of signals to drive circuitry for applicationto a liquid crystal display. Circuit means are provided for producingcurrent sources as load devices in these circuits in lieu of high valueexternal resistors. The current sources receive a regulated referencebias current and thus are independent of supply voltage fluctuations andload changes.

The regulator of the present invention provides such a regulatedreference bias current source. Therefore it is a principal object of thepresent invention to provide a regulator circuit suitable forincorporation into integrated circuits to establish a regulatedreference bias for constant current sources.

Other objects and advantages of the invention will be apparent uponreading the following detailed description of illustrative embodimentsin conjunction with the drawings wherein:

FIG. 1 schematically illustrates a regulator in accordance with thepresent invention to insure that the constant current sources do notfluctuate;

FIG. 1A is the circuit of FIG. I redrawn;

FIG. 2 schematically illustrates a constant current source;

FIG. 3 schematically illustrates a plurality of current sources;

FIG. 4 is a plan view of a current source in accordance with the presentinvention;

FIG. 4A schematically depicts the current source of FIG. 4',

FIG. 5 is a cross-sectional view of the current source illustrated inFIG. 4;

FIG. 6 schematically illustrates a slave regulator which may be utilizedin accordance with the present invention;

In the disclosure of the above-referenced Williams and Schnurrapplication the regulator 16A of FIG. 2 is the system master regulatorand in the illustrated twochip embodiment is connected to a slaveregulator 16B. That is, as illustrated in FIG. 2 of that application.the seconds and minutes counters, decoders. and drivers are defined onone integrated circuit chip while the remaining circuitry is on a secondintegrated circuit chip. Since device parameters may vary from chip tochip, a master/slave regulator system is provided.

The regulator of the present invention is suitable for use as such amaster/slave regulator.

The regulator circuitry in accordance with the present invention isdescribed with reference to FIGS. 1-6.

The basic operation of a current source is depicted in FIG. 2.Transistor Tl defines a reference along with resistor R. Transistor Tlhas its base and collector tied together and forms a diode. The currentthrough this diode forms a voltage reference. The assumption is madethat the base drive required in transistor T1 is small compared to itsemitter current. When transistor T2 is connected as shown in FIG. 2, thepotential established by the base-emitter drop of transistor T1 isplaced across the base-emitter of T2. Therefore, the current that flowsin the emitter of transistor T2 will be the same as that which flows inthe emitter of transistor T1. It is assumed that currents I and 1,, aremuch smaller than the emitter currents l Therefore, the assumption isthat the sum of 1 and I i.e., I is much smaller than the current I Thus,the current 1,, is deter mined by the value of resistor R. Iftransistors T1 and T2 are well-matched, then the collector current I ofT2 will be essentially identical to the current that flows through theresistor R. The practical limitations of this type circuit are apparentin FIG. 3. When the basic current source is extended to have manycurrent sources connected to it, then the assumption which was madeabove that the base current is small compared to the collector currentin the reference section no longer holds. Also, the current that isestablished by the resistor R is directly dependent upon the supplyvoltage V.

In accordance with the present invention, a circuit is provided whichsets a current I in the reference that is independent of supply voltageand also which is independent of the base current from the currentsources I (FIG. 3). The regulator circuit of the present system isillustrated in FIG. I, wherein a fixed current flows in the emitter oftransistor 5.

Operation of the regulator circuit of FIG. I is as follows. The currentI in FIG. 1 is set to be about IS times as large as the current 1,. Thisratio is established by the geometries of transistors l, 2, 3 and 4.This ratio is not critical. Because of the ratio between currents I andI,, the base-emitter voltages of transistor 6 and 7 are different. Thisvoltage difference appears across the external resistor which isconnected to ground and IC chip bonding 23. This resistor may, forexample, be on the order of 68K ohms. Three-fourths of the collectorcurrcnt of rcfcrcncc transistor 5 flows through this resistor to groundsince three of the four collectors are commonly connected thereto. lfthe current flowing through rcfcrcncc transistor 5 becomes too large.the potential acros the resistor will increase. This causes more olt'tltt'ctti l, to go to base drive for transistor 7. Thcrcforc. more ofcurrcnt I: will becon'ic collector current of rrrltnvistor 7. deprivingtransistor 8 of its base vtwho: transistor begins to turn off, itreduces the have time to ail cf the p n-p transistors used as cur-.Tiieictorc. liLllltslEilUl' 5 loses its base drive and its cur .t mustdecrease. If the current in transistor 5 dccrcascs too much. the voltageacross the resistor sill drop dinning morc of the current of l, into the"csistor. This dcpiitcs transistor 7 of base drive and allous moreofcurrent 1 to go to base drive for transistor This. increases me bascdrive to transistor 5 and all of the p-n-p transistors \thich are usedcurrent sources. The regulator circuit has a sufficient dynamic range toadjust itself to a fixed current established solvl by tlic L'tlcrtttlll'clLl'CllLL resistor. The current cst lished is thus independent ofsupply voltage. The itcr uh is connected between the collector and thebase of transistor 7 is used to compensate the regulator and kccp itfrom oscillating. The resistor which is connected in the collector oftransistor 8 is there to prevent SCR action from latching the regulatot.'lransistu's i 10 and the cxtcrnal resistor attached to EC chip bondingpad 31 are used as a starting circuit to guarantee that the regulatorwill start up. One collec 1' goes to IC chips bonding pad 21. Thecurrent out i. int. collector is used as a reference for thc slate cut.guliuui .il Fltj. t: which may be located on .i trciil lC chip.

The circuit t li IA is the circuit of FIG. I redrawn in a iiltlltitil'hat may facilitate the above explanation and better illustrate thefunction of the various devices. in 1. transistors 2, 3, 4 and part of1, inch are all connected in parallel in FIG, 1 are coinbiiicd tor l ite.. the fourth collectorl is shown in FIGv iA as i. Like" c twocollector circuits of transistor 5 are depicted \sith separatetransistors S'A and S'B. Assuming that the geometries to the transistorsof FIG. IA are such that the ratios of currents l and I and cur- ;ciirsi and are ma ntained as in Fifi. l the opera-- tion of thc tvio circuitsis exactly the same.

A schematic; of the slave regulator is illustrated in llC (i.Transistors l3. 14 and i5 form a current source v h 'h is Llli'CL'll}dependent upon the currcnt from the reference node of the masterregulator described in FIG. i. Transistor 13 forms a referencebaseemitter p..itential which then sets the emitter currents in transisrot s 14 and in. 'the difference in the number of :Riittcrs l stuc-cntransist l3 and 14 and transistor l thcic is an 8 to l ratio between thecurrents that lion il the collecto s of transistors 14 and 15.Transistor 12 Q :t rcfcrcnce 2.1115 sior for all of the current sourccscontrolled by slave regulator. its current is established primarily bythe collector current of transisun 15. A small amount ofthe current outofthe Ctll fit.

i'ciit sourc tor Lll trunsis ransistor 12 and he 'tftlic current therebyrcducnig the basedrite to bri: it; its ci l cctor current iT'ilCln in intransistor 12 is too small. then transistor 16 will be deprived of bascdrive. Transistor 17 will then receive additional base drive and it inturn will supply additional base drive for transistor 12. The capacitorbctween the collector and the base of transistor 16 is used tocompensate the regulator and keep it from oscillatmg.

CURRENT SOURCE With reference to FIGS. 4. 4A and 5, a typical fourcollector p-n-p transistor which is used as a current source load inaccordance with the present invention is illustrated. HO. 4 is a planview illustrating the layout ofa typical current source transistor. Forthe illustrated example. a substrate 91 may. by way of example. bccomprised of p-type silicon. A p+ diffusion 88 defines an isolationbarrier between various components on the substrate. The base region ofthe transistor comprises an n-type cpi layer 90. A DUF n-lregion 92 isformed to underlie the transistor structure. An n+ region 94 is formedfor the base contact. Collectors C1, C2. C3 and C4 are formed around acentral p diffused emitter rcgion 96. The transistor is schematicallyillustrated in FIG. 4A. Conventional integrated circuit fabricationtechniques may be utilized in fabricating the transistor structure. Suchtechniques are well-known to those skilled in the art and need not beexplained in detail hcrcin,

While various embodiments have been described in detail herein. it willbe apparent to those skilled in the art that various changes may be madewithout departing from the spirit or scope of the invention.

What is claimed is:

l. A reference bias regulator for a current source comprising.

a. a reference portion having a first bipolar transistor means of onetype connected in emittencollector series with a reference resistorbetwcen first and second reference nodes;

b. a differential regulator portion having second and third bipolartransistor means of said one type and fourth and fifth bipolartransistor means of the opposite type. resistance means and capacitancemeans. the bases of said transistor means of like types being connectedtogether, the emitters of said transistor means of said one type beingconnected together and through said resistance means to the firstreference node and the emitter of said fourth transistor means beingconnected to the second rcfcrcncc node, the collectors of said secondand fourth transistor means being connected together and to one terminalof said capacitance means; the collectors of said third and fifthtransistor means being connected together and to the bases of saidfourth and fifth transistor means and to the other terminal of saidcapacitance means and the emitter of said fifth transistor means beingconnected to the junction of said reference resistor and said firsttransistor means; and

c. a drive portion having a sixth bipolar transistor means of saidopposite type. the base of said sixth trai or means being connected tothe collector of said second and fourth transistor means and the cnuttcrof said sixth transistor means being connected to said second referencenode.

2. The regulator defined in claim 1 wherein said second, third. fourthand fifth transistor means are so arranged and constructed that thecollector current of said second transistor means is greater than aboutfifteen times the collector current of said third transistor means.

3. The regulator as defined in claim 2 further including a start portioncomprising further bipolar transistor means connected to said driveportion and arranged to insure initial start up of said regulator.

4. The regulator as defined in claim 1 further having a slave regulatorportion comprising first, second, third and fourth additional bipolartransistor means of said one type with their emitters connected to oneterminal of a supply voltage, fifth, sixth, seventh, eighth and ninthadditional bipolar transistor means of said other type with theiremitters connected to the other terminal of a supply voltage, andadditional capacitance means; the bases of said fifth, sixth and seventhadditional transistor means and the collector of said fifth additionaltransistor means being connected to the collector of said firstadditional transistor means; the base of said first additionaltransistor means being connected to the base of said first transistormeans; the bases of said second and third additional transistor meansbeing connected to the collectors of said second and sixth additionaltransistor means; the collectors of said fourth and seventh additionaltransistor means being connected to the base of said eighth additionaltransistor means and to one terminal of said additional capacitancemeans; the collector of said third and eighth additional transistormeans being connected to the base of said ninth additional transistormeans and to the other terminal of said additional capacitance means;and the collector of said ninth additional transistor means beingconnected to the base of said fourth additional transistor means.

5. A regulator as defined in claim 4 wherein said second, third, fourthand fifth transistor means are so arranged and constructed that thecollector current of said second transistor means is greater than aboutfifteen times the collector current of said third transistor means andwherein said first transistor means and said first additional transistormeans are so arranged and constructed that the collector current of saidfirst transistor means is more than about three times the collectorcurrent of said first additional transistor means.

6. The regulator as defined in claim 5 further including a start portioncomprising further bipolar transistor means connected to said driveportion and arranged to assure initial start up of said regulator.

7. In a reference bias regulator for constant current sources wherein amaster regulator output is taken from the base of a reference bipolartransistor means of one type connected in emitter-collector series witha reference resistor between the terminals of a voltage source. a slaveregulator comprising:

first, second, third and furth bipolar transistor means of said one typewith their emitters connected to one terminal of the supply voltagesource. fifth. sixth, seventh, eighth and ninth bipolar transistor meansof said other type with their emitters connected to the other terminalof said supply voltage source and capacitance means; the bases of saidfifth, sixth and seventh transistor means and the collector of saidfifth transistor means being connected to the collector of said firsttransistor means, the base of said first transistor means beingconnected to the base of said reference transistor, the bases of saidsecond and third transistor means being connected to the collectors ofsaid second and sixth transistor means, the collectors of said fourthand seventh transistor means being connected to the base of said eighthtransistor means and to one terminal of said capacitance means, thecollectors of said third and eighth transistor means being connected tothe base of said ninth transistor means and to the other terminal ofsaid capacitance means, and the collector of said ninth transistor meansbeing connected to the base of said fourth transistor means.

8. A regulator as defined in claim 7 wherein said first transistor meansis so arranged and constructed as to have a collector current less thanabout one-third, the

collector current of said reference transistor means.

1. A reference bias regulator for a current source comprising: a. a reference portion having a first bipolar transistor means of one type connected in emitter-collector series with a reference resistor between first and second reference nodes; b. a differential regulator portion having second and third bipolar transistor means of said one type and fourth and fifth bipolar transistor means of the opposite type, resistance means and capacitance means, the bases of said transistor means of like types being connected together, the emitters of said transistor means of said one type being connected together and through said resistance means to the first reference node and the emitter of said fourth transistor means being connected to the second reference node, the collectors of said second and fourth transistor means being connected together and to one terminal of said capacitance means; the collectors of said third and fifth transistor means being connected together and to the bases of said fourth and fifth transistor means and to the other terminal of said capacitance means and the emitter of said fifth transistor means being connected to the junction of said reference resistor and said first transistor means; and c. a drive portion having a sixth bipolar transistor means of said opposite type, the base of said sixth transistor means being connected to the collector of said second and fourth transistor means and the emitter of said sixth transistor means being connected to said second reference node.
 2. The regulator as defined in claim 1 wherein said second, third, fourth and fifth transistor means are so arranged and constructed that the collector current of said second transistor means is greater than about fifteen times the collector current of said third transistor means.
 3. The regulator as defined in claim 2 further including a start portion comprising further bipolar transistor means connected to said drive portion and arranged to insure initial start up of said regulator.
 4. The regulator as defined in claim 1 further having a slave regulator portion comprising first, second, third and fourth additional bipolar transistor means of said one type with their emitters connected to one terminal of a supply voltage, fifth, sixth, seventh, eighth and ninth additional bipolar transistor means of said other type with their emitters connected to the other terminal Of a supply voltage, and additional capacitance means; the bases of said fifth, sixth and seventh additional transistor means and the collector of said fifth additional transistor means being connected to the collector of said first additional transistor means; the base of said first additional transistor means being connected to the base of said first transistor means; the bases of said second and third additional transistor means being connected to the collectors of said second and sixth additional transistor means; the collectors of said fourth and seventh additional transistor means being connected to the base of said eighth additional transistor means and to one terminal of said additional capacitance means; the collector of said third and eighth additional transistor means being connected to the base of said ninth additional transistor means and to the other terminal of said additional capacitance means; and the collector of said ninth additional transistor means being connected to the base of said fourth additional transistor means.
 5. A regulator as defined in claim 4 wherein said second, third, fourth and fifth transistor means are so arranged and constructed that the collector current of said second transistor means is greater than about fifteen times the collector current of said third transistor means and wherein said first transistor means and said first additional transistor means are so arranged and constructed that the collector current of said first transistor means is more than about three times the collector current of said first additional transistor means.
 6. The regulator as defined in claim 5 further including a start portion comprising further bipolar transistor means connected to said drive portion and arranged to assure initial start up of said regulator.
 7. In a reference bias regulator for constant current sources wherein a master regulator output is taken from the base of a reference bipolar transistor means of one type connected in emitter-collector series with a reference resistor between the terminals of a voltage source, a slave regulator comprising: first, second, third and furth bipolar transistor means of said one type with their emitters connected to one terminal of the supply voltage source, fifth, sixth, seventh, eighth and ninth bipolar transistor means of said other type with their emitters connected to the other terminal of said supply voltage source and capacitance means; the bases of said fifth, sixth and seventh transistor means and the collector of said fifth transistor means being connected to the collector of said first transistor means, the base of said first transistor means being connected to the base of said reference transistor, the bases of said second and third transistor means being connected to the collectors of said second and sixth transistor means, the collectors of said fourth and seventh transistor means being connected to the base of said eighth transistor means and to one terminal of said capacitance means, the collectors of said third and eighth transistor means being connected to the base of said ninth transistor means and to the other terminal of said capacitance means, and the collector of said ninth transistor means being connected to the base of said fourth transistor means.
 8. A regulator as defined in claim 7 wherein said first transistor means is so arranged and constructed as to have a collector current less than about one-third, the collector current of said reference transistor means. 